Many ophthalmic devices, including contact lenses, surgical lenses, intraocular lenses, and the like, are often made by performing a polymerization reaction within a casting cup assembly. The casting cup assembly includes a basecurve mold, which forms the portion of the device that rests against the eye, and a frontcurve mold, which forms the portion of the device facing away from the eye. A reaction mixture, which includes one or more polymerizable monomers and other components, is disposed in the frontcurve mold. Thereafter, the basecurve mold is pressed against the frontcurve mold and the reaction mixture is forced to adopt the shape of the volume defined between the two molds. After properly being positioned, the reaction mixture is subjected to polymerization conditions (e.g. photopolymerization or other suitable technique). The resulting polymer is removed from the casting cup assembly and subjected to post-polymerization processing (e.g. rinsing, hydration, etc) to provide a finished ophthalmic device. Separation of the lens from the mold assembly requires accurate and precise prying of the lens mold halves apart to release the cast contact lens. Precise automated prying mechanisms are employed and the repeated operation of this step is a critical factor in maintaining high yields of lenses that meet the requirements of the lens design.
During this post-polymerization processing, careful inspection of the lenses often reveals a substantial number of the lenses contain defects. Defects include a variety of fabrication errors such as holes in the lenses, tears in the edges, the presence rings of excess polymer around the ophthalmic device, and other similar defects. Therefore, an improved casing cup assembly that allows repeatable and precise opening of the lens mold assemblies and prevents excess flash material from interfering with the prying mechanisms is desired to reduce the occurrence of these defects.
In U.S. Pat. No. 5,540,410 incorporated herein by reference are disclosed molds and their use in contact lens manufacture. With all cast molding methods the manufacture of lenses that meet the intended design parameters is the key goal and is difficult to obtain with complete accuracy given the very precise design parameters that are called for, slight variation in the thickness and contour of the lens, especially relating to its optical zone, and clean edges that show no signs of tears or deformation. In addition, other various approaches to lens mold design have been developed over time. For instance, U.S. Pat. No. 6,997,428 shows the use of tabs to align optical surface and that may also be used to pull the mold halves apart. There is no indication that the tabs are used to deliver melt or to provide plane offset between the mold portions.
U.S. Pat. No. 5,252,056 illustrates a process that uses rotationally symmetric parts and which does not use a blade as a means for having a hot runner run through the blade to improve injection flow by broadening the injection front. U.S. Pat. No. 5,254,000 teaches small tabs for interlocking mold halves and U.S. Pat. No. 6,444,145 uses one blade rather than the four of the present invention.
None of the references use multiple blades to deliver monomer on a broadened injection front and to improve the separation of mold halves after curing.